Yarrow is a web front end to the RGTP bulletin board transfer protocol used on the Cambridge GROGGS forums.

RGTP is:
* secure (users are cryptographically identified)
* centralised (all discussion is held on one server under the control of nominated editors)
* linear (the item format helps regulate thread drift)
* mature (it has been in regular use for over fourteen years).

Yarrow is:
* convenient (it can be used on any computer which can run a web browser)
* stable (it has been in regular use on several sites for seven years)
* safe (all state is held on one server, rather than being passed over the net)
* free (the source is openly available, and licensed under the GPL).